Enforce constraints on @Value annotated field in Spring Boot application

Question

I have the following field annotated with @Value, specifying a default value:

@Value(\"${tolerance.percentage:25}\")
private int tolerance;


        

Answer 1

Validation using regular validation API annotations is only going to work in certain circumstances.

1. You have an implementation ('hibernate-validator') on the classpath
2. The class they are in are used to bind externalized configuration

So instead of using @Value with those you probably want to create a class that contains the expected properties and use binding with @ConfigurationProperties. (and you might want to use @Range instead).

@ConfigurationProperties(prefix="tolerance")
public ToleranceProperties {

    @Range(min=1, max=100)
    private int percentage = 25; 

    // Here be a getter/setter
}

This combined on a @Configuration class add @ EnableConfigurationProperties(ToleranceProperties.class) and you can use it anywhere you need properties. (See typesafe configuration properties in the reference guide.

Note: You could also declare it as a @Component.